The present invention relates to a combination instrument useful both for examining the eye and for treating the eye. It comprises a stereoscopic viewing microscope and an associated unit.
One form of ophthalmological combination instrument is disclosed in German Federal Republic Pat. No. 26 14 273 (Carl Zeiss), of Feb. 15, 1979, and its similar British Pat. No. 1,575,244, of Sept. 17, 1980. That instrument comprises a diagnostic instrument in which a slit lamp, constructed in accordance with the principle of a binocular telescope magnifier, can be converted into an ophthalmometer by the insertion of another optical part after removal of the main objective of the stereoscopic viewing microscope.
It is also known to provide an operation microscope which can be combined with a laser system for purposes of treatment. Such instruments are disclosed, for example, in U.S. Pat. No. 3,096,767 (Gresser et al.) of July 9, 1963, and U.S. Pat. No. 3,769,963 (Goldman et al.) of Nov. 6, 1973. In these two patents, the therapeutic laser radiation is guided outside the viewing instrument or operation microscope.
If one attempts to combine a laser system for therapy purposes with a stereoscopic viewing microscope, according to the combining principles disclosed in the above mentioned German Pat. No. 26 14 273, there would have to be available a laser of small size, the radiation of which can be conducted through the viewing lens system of the binocular viewing microscope. Surprisingly, it has been found that a laser which is particularly well suited for this purpose is a neodymium-yag pulse laser (Nd:yag laser), known from range finder systems, which has a passive quality switch (Q switch). This known laser has the characteristic that upon an increase in the intensity of the pumping light it emits, in one pulse sequence, not just one individual pulse, but rather a pulse chain of several (e.g., up to five) individual pulses, the time spacing beteen the pulses being 10 to 2.mu. sec and the energy of the individual pulses being about 15 to 10 mJ.
For the previous field of use of this known laser (i.e., in rangefinder systems), this property is undesired, and is avoided by suitable selection of the operating conditions. However, this property has been found to be useful for the treatment of cataracts of the eye. Such laser pulses produce, upon focusing, spontaneous ionization of the material and thereby destroy the protein fibrils which cause clouding of the lens or vitreous body of the eye.
It has been found that, for proper guidance of the therapeutic effect, specifically this spontaneous collapse of material and the mechanical shock wave connected therewith which leads to the cracking of the protein fibrils are the important factors. The above mentioned Nd:yag laser is excellently suited for the intended therapeutic purpose when it is operated with a sufficiently high pumping-light energy. Likewise, this laser can also be used to advantage for perforating the lens membrane or the iris itself.